1. Field of the Invention
The present invention relates to a shifting apparatus for a multispeed bicycle having a plurality of front chainwheels, a plurality of rear gears, and front and rear derailleurs. This shifting apparatus is operable with a single manual lever to actuate the two derailleurs.
2. Description of the Prior Art
A known shifting apparatus for a multispeed bicycle as noted above is disclosed in U.S. Patent No. 4,194,408, for example. The bicycle has two front chainwheels, five rear gears, and front and rear derailleurs for changing a chain among these chainwheels and gears. The shifting apparatus includes a pair of change speed cams rotatable by a single manual lever, a pivot link pivotable by one of the change speed cams to pull or relax a control cable connected to the front derailleur, and a pivot link pivotable by the other change speed cam to pull or relax a control cable connected to the rear derailleur. When the manual lever is operated, the pair of change speed cams cause one or both of the derailleurs to change the chain among the front chainwheels and/or rear gears. Thus, the shifting apparatus provides 10 speed stages.
With an operation of the shifting apparatus, the chain may be changed both between the front chainwheels and between the rear gears. For example, the chain may be changed from the smaller front chainwheel to the larger front chainwheel and from the smallest rear gear to the largest rear gear, or from the larger front chainwheel to the smaller front chainwheel and from the largest rear gear to the smallest rear gear. A relatively long time is required to complete the actual shifting operation. For an interval of time must be set between the change at the front and the change at the rear, e.g. the chain is changed at the front and thereafter at the rear. This is necessary to avoid the chain coming off the chainwheels or gears which tends to occur when the chain is changed simultaneously at the front and the rear.